Method and structure for providing improved thermal conduction for silicon semiconductor devices

ABSTRACT

Thermal cooling structures of diamond or diamond-like materials are provided for conducting heat away from semiconductor devices. A first silicon-on-insulator embodiment comprises a plurality of thermal paths, formed after shallow trench and device fabrication steps are completed, which extend through the buried oxide and provide heat dissipation through to the underlying bulk silicon substrate. The thermal conduction path material is preferably diamond which has high thermal conductivity with low electrical conductivity. A second diamond trench cooling structure, formed after device fabrication has been completed, comprises diamond shallow trenches disposed between the devices and extending through the buried oxide layer. An alternative diamond thermal cooling structure includes a diamond insulation layer deposited over the semiconductor devices in either an SOI or bulk silicon structure. Yet another embodiment comprises diamond sidewalls formed along the device walls in thermal contact with the device junctions to provide heat dissipation through the device junctions to underlying cooling structures. It is also proposed that the foregoing structures, and combinations of the foregoing structures, could be used in conjunction with other known cooling schemes.

FIELD OF THE INVENTION

This invention relates to semiconductor device cooling and, moreparticularly, to a method and structure for providing CVD diamondthermal conduction structures for semiconductor devices.

BACKGROUND OF THE INVENTION

Semiconductor chips require cooling to sustain reliability of circuitsand interconnects formed on and in the semiconductor chips, to optimizecircuit switching performance, and to suppress thermally generated noisein the circuits. An increased need for thermal cooling is seen for CMOStransistors, wherein high temperatures yield significantly largerleakage currents due to thermal generation of carriers. Moreover, asdevice dimensions decrease, leakage current grows exponentially.

As a result, a myriad of cooling structures have been devised forincorporation into the semiconductor chip structure itself and for usewith semiconductor chip structures. Cooling may be provided for anentire circuit board, may be applied selectively to individual chips, ormay be provided on-chip to dissipate heat from individual hot spotswithin a chip. Examples of some prior art cooling solutions include U.S.Pat. No. 5,621,616 of A. H. Owens, wherein a high conductivity thermaltransfer pathway is created, using multiple metal layers and vias, todraw heat away from the bulk silicon semiconductor substrate. Owensadditionally proposes embedding metal plugs into a chip substrate tocollect heat generated by transistors and remove the heat through metalinterconnects in the chips.

Silicon-on-insulator (SOI) structures for CMOS devices have beendeveloped as an alternative to the bulk silicon device technology forvery large scale integration (VLSI) circuits. The SOI structures arepreferable due to the advantages provided by the buried oxide (BOX)insulator layer. The BOX advantages include an absence of the reversebody effect, absence of latch-up, soft error immunity, and eliminationof the parasitic junction capacitance typically encountered in bulksilicon devices. Reduction of the parasitic capacitance allows forgreater circuit density, operation at higher circuit speeds, and reducedpower consumption.

FIG. 1 illustrates a typical SOI CMOS structure wherein buried oxide(BOX) layer 103, generally about 0.1-0.5 microns in thickness, isprovided in the substrate 101, which comprises 400-600 microns ofsilicon. For the sake of illustration, silicon-on-oxide (SOI) layer 105is shown as a p-type silicon substrate having a thickness of about 0.2-1μm, with an NMOSFET device 104 formed at the surface. Clearly, theensuing description of both the background and the novel structure andmethod will be equally applicable to devices formed in an n-type SOIsilicon substrate. The NMOSFET device 104, formed in the SOI layer abovethe buried oxide layer, comprises polysilicon gate 106 and source anddrain regions 109. Adjacent NMOSFET devices are both physically andelectrically isolated from each other by shallow trench regions 108,typically comprised of an oxide region.

While SOI structures are advantageous for reduction of parasiticcapacitance otherwise associated with bulk silicon CMOS devices, thereare disadvantages to the isolation provided by the buried oxide layer.With the isolation provided by the buried oxide, the devices cannotdissipate heat to the 400-600 micron silicon substrate, as efficientlyas devices formed on bulk silicon had allowed, since the BOX is athermal barrier.

One structure which has been proposed for SOI cooling is presented inU.S. patent application Ser. No. 08/822,440, entitled“Silicon-On-Insulator Structure for Electrostatic Discharge Protectionand Improved Heat Dissipation” which was filed on Mar. 21, 1997 and isassigned to the present assignee. In that application, the contents ofwhich are incorporated by reference herein, thermally conductive plugsare formed passing through the buried oxide region and into the oppositetype silicon substrate. The plugs, preferably comprising polysilicon,are in contact with the sources and drains of the CMOS devices toprovide paths for dissipating positive and negative ESD stresses, inaddition to providing thermal dissipation pathways for directing heataway from the circuitry.

Yet another proposed solution is found in U.S. patent application Ser.No. 09/006,575, of Joshi, et al, entitled “Embedded Thermal Conductorsfor Semiconductor Chips”, filed on Jan. 13, 1998 and currently underallowance, and its divisional case Ser. No. 09/296,846 filed Apr. 22,1999, both of which are assigned to the present assignee. In accordancewith the teachings of those applications, the contents of which areincorporated by reference herein, back-side diamond thermal paths areprovided effectively to act as cooling fins; or alternatively,front-side shallow trench diamond thermal conductors are provided incontact with the devices at the substrate surface and extend through theBOX layer to contact the underlying bulk silicon. The shallow trenchdiamond structures provide both electrical isolation between devices andthermal conduction of heat away from the devices. A disadvantage to theformer Joshi structure is that back-side cooling does nothing fordissipating heat away from the front-side-mounted devices. Adisadvantage to the latter Joshi front-side structure and method is thatthe trenches are formed prior to device fabrication. As a result, thediamond in the trenches must be recessed and covered to protect it fromthe subsequent processing steps; thereby requiring numerous additionalprocessing steps and resulting in an unusual structural profile.

It is therefore an objective of the present invention to provideimproved cooling through thermal conduction structures for semiconductordevices.

It is additionally an objective of the invention to provide a method forcreating thermal conduction paths for SOI devices on the front side ofthe wafer.

Yet another objective of the invention is to provide a method forincorporating thermal conduction paths into SOI structures which iscompatible with currently-used SOI fabrication processes.

SUMMARY OF THE INVENTION

These and other objectives are realized by the present inventionincluding a first silicon-on-insulator embodiment which comprises aplurality of thermal paths, formed after shallow trench and devicefabrication steps are completed, which extend through the buried oxideand provide heat dissipation through to the underlying bulk siliconsubstrate. The thermal conduction path material is preferably diamondwhich has high thermal conductivity with low electrical conductivity. Asecond diamond trench cooling structure, formed after device fabricationhas been completed, comprises diamond shallow trenches disposed betweenthe devices and extending through the buried oxide layer. Similardiamond trench structures can be implemented when forming semiconductorsin bulk silicon. An alternative diamond thermal cooling structureincludes a diamond insulation layer deposited over the semiconductordevices. For transistors, yet another embodiment comprises diamondsidewalls formed along the gate walls in thermal contact with the devicejunctions to provide heat dissipation through the device junctions tounderlying cooling structures. Diamond sidewalls may also be used forchanneling heat from other semiconductor devices and from interconnectwiring disposed at the substrate surface. It is also proposed that theforegoing structures, and combinations of the foregoing structures,could be used in conjunction with other known cooling schemes such asthe backside diamond cooling fins taught by the aforementioned Joshi, etal patent and patent application.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be detailed with specific reference to theappended drawings of which:

FIG. 1 provides a schematic illustration of a typical prior art SOIstructure.

FIG. 2 illustrates a proposed CVD diamond thermal path structure for SOIapplications in accordance with the present invention.

FIGS. 3A through 3G show processing steps for fabricating the structureof FIG. 2.

FIG. 4 illustrates an embodiment of the present invention comprisingdiamond filled shallow trench regions between devices.

FIG. 5 illustrates the semiconductor structure of FIG. 2 furtherincluding a diamond insulation layer as taught by the present invention.

FIGS. 6A through 6C illustrate embodiments of the present inventionincluding diamond sidewall spacers.

FIGS. 7A through 7F show processing steps for providing inventivediamond cooling structures using a diamond layer for self-aligned devicefabrication.

FIGS. 8A and 8B provide illustration of a thermal analysis conducted ofsemiconductor structures formed in accordance with the prior art and thepresent invention, respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention provides semiconductor cooling structures whichare superior to those found in the prior art. The cooling structuresinclude a first embodiment comprising thermal conduction paths formed ina silicon-on-insulator (SOI) structure having a buried oxide (BOX)layer, where the thermal conduction paths are formed between the shallowtrench layers which isolate device and extend through the BOX layer tocontact the underlying silicon. A second implementation of the inventionprovides for formation of diamond shallow trench regions between devicesafter device fabrication has been completed, either on an SOI or a bulksilicon structure. Under such an embodiment, more effective thermalconduction paths can be provided in the shallow trenches since thediamond would not require silicon nitride and oxide overlayers toprotect it from subsequent thermal oxidation steps. Another embodimentincludes a planar, thermally conductive insulation layer disposed overthe completed device structures and having openings for device contact.The thermally conductive insulation layer can laterally direct heat awayfrom the devices and toward cooling structures. Yet anotherimplementation comprises thermally conductive sidewall spacers areprovided along the vertical sides of devices, metal wiring and/or metalvias to provide heat dissipation. The sidewall spacer embodiment ispreferably implemented on a bulk silicon structure, but may also be usedon an SOI structure, preferably in conjunction with another coolingmeans.

All of the foregoing thermal conductors are preferably fabricated ofdiamond or diamond-like materials, for example diamond-like carbon orsilicon carbide (hereinafter collectivley referred to as “diamond”).Diamond has a high thermal conductivity, which is more than 14 timesthat of silicon, and is an electrical insulator. Diamond also adhereswell to silicon. The properties of chemical vapor deposited (CVD)diamond are given in Table 1, as compared to those properties forsilicon and silicon dioxide:

TABLE 1 MATERIAL PROPERTIES Diamond Silicon Silicon Dioxide Thermal1000-2000 110-150 0.1 to 1.5 conductivity (W/m-K) Dielectric 5.7 — 3.9constant (CTE) TCE 2.8 3.5 0.55 (×10⁻⁶ cm/° C.

As taught in the aforementioned Joshi, et al patent applications, a hotwall filament chemical vapor deposition system may be used to processdiamond to create films. Diamond films may be deposited using a gasmixture of CH₄ and H₂ under high pressure, for example 30-40 Torr,varying the temperature from 600-1100° C. The gas mixture may includeabout 10-30% volume CH₄ and about 70-90% H₂, although other gases may bepresent.

While diamond layers can be blanket deposited and subsequently etchedusing reactive ion etching, the features or depressions in Si or SiO₂contribute to defects which form good nucleation sites for depositeddiamond. Surfaces having defects act as nucleation sites whereby thedeposition can be selective with respect to surfaces having no defectareas. Therefore, the CVD diamond filling of an opening may start at thebottom or corners of trenches, as these areas form nuclei with lowerfree energy of formation.

Alternative methods for depositing polycrystalline diamond on singlecrystalline silicon include a microwave plasma system, an RF plasmasystem which is inductively or capacitively coupled, and a directcurrent plasma system. U.S. Pat. No. 4,981,818 provides teachingsrelating to the tuning or matching of networks required for electricallycoupling electrical energy to generated plasma when depositing diamondusing either the RF or microwave plasma systems. European patentapplication 286396 additionally provides examples of methods for growingpolycrystalline diamond on top of single crystal silicon.

FIG. 1, as discussed above, illustrates one embodiment of circuitryfabricated using silicon-on-insulator (SOI) technology, for which thecooling can be greatly improved by the present invention. For example,the n-type MOSFET devices 104 of FIG. 1, comprised of gates 106 andsource and drain regions 109, are isolated from the bulk siliconsubstrate 101 by the buried oxide layer 103 and are isolated from eachother by the shallow trench regions 108. The features which provideadvantages to the SOI configuration over bulk devices, such as thesuperior isolation from parasitic capacitance from the bulk silicon,also give rise to disadvantages, such as lack of an efficient conductionpath for dissipation of power and heat from the device regions to thesubstrate.

FIG. 2 illustrates a proposed CVD diamond thermal path structure for SOIapplications in accordance with the present invention. Silicon substrate201 has a buried oxide layer (BOX) 203 formed therein, with siliconlayer 205 disposed over the BOX layer. Dielectric-filled shallowtrenches 208 are formed in silicon layer 205, with devices 204 formed inthe silicon layer 205 between the shallow trenches 208, and dielectriclayer 212 formed at the surface, in accordance with the prior art. Underthe present invention, diamond thermal conduction paths 210 are formedbetween the shallow trench regions 208 and extend through the siliconlayer 205 and through the BOX layer 203 to contact the underlyingsilicon of substrate 201. Heat generated by devices 204 will beconducted away from the devices through the diamond paths 210 to theunderlying bulk silicon, which may include additional cooling structures(not shown) for cooling. It is to be noted that the thermal conductionpaths will also conduct trapped heat from the silicon layer 205 and heatgenerated by wiring located at the semiconductor structure surface. Asone alternative to the illustrated structure, diamond may be used tofill the shallow trench regions between devices formed in either a bulksilicon or 501 substrate, alone or in conjunction with thediamond-filled deep trenches of FIG. 2.

FIGS. 3A through 3G show processing steps for fabricating the structureof FIG. 2. In FIG. 3A, silicon substrate 201 is shown including BOXlayer 203 and silicon layer 205 which is etched to provide shallowtrench openings 300. As shown in FIG. 3B the shallow trench openings 300are filled with an appropriate dielectric to form shallow trenches 208which provide electrical isolation between adjacent devices which are tobe formed. The fabrication of device 204 is shown in FIGS. 3C through3E, including formation of gate 306, masking of gate 306 with layer 308to protect the gate from the next stage of processing, and implantationof dopants to form source and drain regions 309 in silicon layer 205adjacent to and contacting gate 306. After the devices have beenfabricated, a dielectric layer 312 such as CVD oxide or doped glass isdeposited and planarized. As shown in FIG. 3F, openings 310 for thethermal conduction paths are etched through dielectric layer 312,through silicon layer 205, and through the BOX layer 203, to contact theunderlying silicon of 201. It is preferable to overetch the openingsinto the silicon to ensure that all of the BOX layer is removed in theopenings 310. Thereafter, the openings 310 are filled to form thethermal conduction paths 210. Diamond or other diamond like substances,as discussed above, are recommended for formation of the thermalconduction paths 210, due to their superior thermal conductivity and lowelectrical conductivity. If diamond is to be deposited, then a thermaloxidation step should be carried out after etching of the openings 310.The oxide will prevent direct contact between the diamond and the activedevice areas, thereby preventing unwanted effects such as out-gassing,adhesion failure, etc. Hot filament CVD using a gas mixture of methane(CH₄) and hydrogen (H₂) under high pressure, or one of the other methodsmentioned above, is used to form the diamond thermal conduction paths210 as shown in the finished structure of FIG. 3G. If needed, excessdiamond material is removed by chemical-mechanical polishing or byplasma etching in a reactive ion etching environment with oxygen usingsilicon oxide/nitride hard masks to protect the diamond in the trenches.

The foregoing process may be modified to provide an alternativeembodiment of the invention, as illustrated in FIG. 4. Under theinventive method, prior to device fabrication the areas in which shallowtrenches are to be formed are masked. The masking may be done bydepositing and patterning a layer, such as CVD silicon nitride oroxynitride. Alternatively, shallow trenches may be formed and filledwith CVD oxide which will be removed in a later step and replaced withdiamond. Device fabrication proceeds as above, with formation of device406 including the steps of deposition of the gate 408 and implantationof the source and drain regions 409 in silicon layer 405. After devicefabrication has been completed, the material in the shallow trench areasis removed using a mask, while gate 408 is protected by a protectivefilm 412 (e.g., nitride). The shallow trench openings are etchedcompletely through the silicon layer 405 and BOX layer 403 to contactthe underlying silicon 401, with overetching into the silicon as apreferred step. Thereafter, the shallow trench openings are filled bydeposition of diamond or diamond-like material, as above, to form theshallow trenches 410 which will carry heat from the abutting devices,through the silicon and BOX layers to be dissipated in the underlyingbulk silicon. While the cited Joshi, et al patent and patent applicationteach the use of diamond in shallow trenches, the Joshi, et al methodrequires that the diamond in the shallow trenches be covered by siliconnitride and oxide layers in order to protect the diamond from subsequentgate oxidation. As a result, the Joshi, et al structure is less thanoptimal since the nitride and oxide compromise the thermal conductivityof the structure. By the present inventive method, an inventivestructure is realized wherein the shallow trench is completely filledwith diamond for superior thermal conductivity. A thermal analysis isprovided below with reference to FIGS. 8A and 8B.

FIG. 5 illustrates the semiconductor structure of FIG. 2 furtherincluding a diamond or silicon carbide insulation layer 214 as taught bythe present invention. The diamond insulation layer 214 is deposited, inaccordance with any of the aforementioned methods, in a blanket layer atthe surface of the semiconductor structure and at sufficient depth toform a planar layer with the top surface of the gate 306. Deposition toa greater depth, followed by planarization to expose the gate, ispreferable to ensure a planar surface for the diamond insulation layer.It is here to be noted that the use of a diamond-like material, such assilicon carbide, which is more readily etched back, may be preferablehere. A diamond or diamond-like material insulation layer, like layer214, will aid in conducting heat laterally away from the devices andwill channel that heat toward the thermal conduction paths 210 and outthrough bulk silicon 201 and/or toward a metal interconnect and viathermal conduction path (not shown) formed above the device (as taughtin the prior art, for example, the Joshi, et al patent and patentapplication cited above). A diamond insulation layer may alternativelybe provided on the top surface of a semiconductor structure with deviceswhich have been formed in bulk silicon, as opposed to the illustratedSOI embodiment. While devices formed on bulk silicon generally do notsuffer the extreme adverse thermal effects experienced by devices formedin an SOI structure, a lateral thermal conduction path provided by adiamond insulation film may be increasingly necessary as devicedimensions continue to shrink.

FIGS. 6A provides an illustration of a further alternative embodiment ofthe present invention wherein diamond sidewall spacers are provided tothe gate structure to direct heat away from the gate through the devicejunctions. CVD diamond sidewall spacers 601 are formed over a thermaloxide layer 603 along the sidewalls of gate 606. The preferred methodfor forming the sidewalls is to blanket deposit a diamond layer and etchback the diamond in oxygen plasma with an anisotropic etch. A pair ofsidewall spacers would be formed on both sides of the gate, since theplasma will not etch anything other than the diamond. Once the sidewallspacers have been formed, they will facilitate conduction of heat awayfrom the gate and through the source and drain junction areas 609.Thermal oxide layer 603 provides the necessary barrier between theactive device regions and the deposited diamond material, much like theprotective oxide from the thermal oxidation step discussed above withreference to FIGS. 3A through 3G.

The sidewall spacer embodiment can be implemented on either bulk siliconor SOI structures. Moreover, the sidewall spacers can be used forproviding cooling for structures other than the gate of a transistor asillustrated in FIG. 6A. Highly resistive polysilicon resistors andsurface wiring are structures for which a sidewall spacer could providecooling. FIG. 6B illustrates the use of sidewall spacers 611 disposedalong the sidewalls of metal wiring 616 at the substrate surface. Yetanother embodiment is illustrated in FIG. 6C wherein diamond sidewallspacers 652 are disposed along the sides of openings in dielectric layer650, into which metal interconnects 655 are deposited to contact themetal underlayer 675.

FIGS. 7A through 7F show processing steps for providing inventivediamond cooling structures using a diamond layer for self-aligneddevice, specifically transistor, fabrication on a silicon substratewhich includes top silicon layer 205, buried oxide layer 203 andunderlying bulk silicon 201. As depicted in FIG. 7A, after formation ofgate 706, a blanket layer of diamond is deposited and patterned, leavingdiamond features 700 at the substrate surface and diamond sidewallspacers 701 along the sidewalls of gate 106. The diamond features 700which remains at the surface are disposed over those areas which havebeen designated to include isolation regions between devices. It is tobe noted that the sidewall spacers 701 could be formed in a separateseries of steps whereby either diamond or another dielectric materialcould be deposited over gate 706 and diamond features 700 and thenetched back, leaving sidewall spacers 701 along the gate sidewalls, andsidewall spacers (not shown) along the sidewalls of the diamond features700 as well. After formation of the sidewalls, using the diamond as aself-aligned mask, the source and drain regions 709 are implanted, asshown in FIG. 7B. Next, a dielectric layer 712, such as silicon nitride,is deposited as shown in FIG. 7C. The diamond 700 is removed from thesubstrate surface, as shown in FIG. 7D, and etching into the substrateis conducted to form the trenches 711 into which diamond will bedeposited to form the cooling structures. FIG. 7E shows a finishedcooling structure wherein shallow trench regions have been opened, byremoval of diamond 700 and etching into silicon top layer 205, followedby deposition of diamond into the shallow trench regions to formisolation and cooling structures 710. Alternatively, FIG. 7F shows afinished cooling structure wherein deep trench regions have been opened,by removal of diamond 700 and etching through silicon top layer 205,through buried oxide layer 203 and into contact with underlying silicon201, followed by deposition of diamond into the deep trench regions toform isolation and cooling structures 715.

FIGS. 8A and 8B provide illustration of a thermal analysis conducted ontwo semiconductor structures, a prior art structure and the structure ofthe present invention, respectively. The structure of FIG. 8A includes asilicon dioxide region 804 formed in a 1500 Å silicon layer 805 disposedabove a 3000 Å buried oxide layer 803 with 1 micron of underlying bulksilicon 801. The structure of FIG. 8B includes a CVD diamond region 810formed in 30% of the 1500 Å silicon layer 805 and extending through the3000 Å buried oxide layer 803 to contact the 1 micron of underlying bulksilicon 801. Under the same thermal conditions, the thermal analysisshows that the junction temperature for the structure having a silicondioxide region 804 was 343.1° K., while the junction temperature for thestructure having a CVD diamond insulator region 810 was 302.4° K.Clearly, the CVD diamond region provided a dramatic reduction oftemperature at the junction by dissipating the heat through thestructure. It is asserted that even the relatively small area of diamondprovided in the sidewall spacer embodiment will provide roughly 20× theheat dissipation of that realized by a spacer made of silicon dioxide.

While the present invention has been described with reference to severalpreferred materials and structures, modifications by one skilled in theart cannot be made without departing from the spirit and scope of theinvention as set forth in the appended claims.

Having thus described our invention, what we claim as new and desire tosecure by Letters Patent is:
 1. A semiconductor structure formed in asubstrate comprising silicon comprising: a plurality of semiconductordevices formed in the silicon substrate from a top surface of thesubstrate to a first device depth; a plurality of independent diamondfilled thermal trenches disposed in the substrate adjacent to saiddevices and extending from a top surface of the substrate at which saidplurality of devices are formed and into the substrate to a depth belowsaid device depth to conduct heat away from the plurality of devices anda plurality of diamond sidewall spacers disposed at the sidewalls of thedevices. 2.The structure of claim 1 further comprising a diamondinsulation layer formed at the top surface of the silicon substrate. 3.The structure of claim 1 wherein said substrate comprises a top siliconlayer, a buried oxide layer underlying the top silicon layer, and a bulksilicon region underlying the buried oxide layer and wherein thetrenches extend from the top surface of the silicon top layer, throughthe buried oxide layer, and to the bulk silicon region and are inthermal contact with the devices.
 4. The structure of claim 1 furthercomprising a plurality of shallow trench regions formed in the silicontop layer adjacent the plurality of thermal trenches, each of theplurality of shallow trench regions being positioned between a deviceand a thermal trench.
 5. The structure of claim 4 wherein each of theplurality fo shallow trench regions are filled with diamond.
 6. Thestructure of claim 1 further comprising a plurality of metalinterconnect structures deposited at the substrate surface and incontact with the devices, and further comprising a plurality of diamondsidewall spacers disposed at the sidewalls of the metal interconnectstructures.
 7. The structure of claim 4 further comprising a diamondinsulation layer disposed adjacent to each of the plurality of devicesat the top surface of the silicon substrate.
 8. A semiconductorstructure formed in a silicon substrate having a top layer comprising: aplurality of transistors each comprising a source region and a drainregion formed in said top layer of said silicon substrate and a gateformed over the source and drain regions; and a plurality of thermallyconductive diamond sidewall spacers disposed at sidewalls of each gateand contacting the source and drain regions.
 9. The structure of claim 8further comprising a plurality of trench regions formed in the siliconsubstrate, each of the plurality of trench regions being filled withelectrically nonconductive material and being positioned betweenadjacent transistors.
 10. The structure of claim 8 wherein theelectrically nonconductive material comprises diamond.
 11. The structureof claim 8 further comprising a diamond insulation layer formed adjacentto the diamond sidewall spacers at the sidewalls of the gates of each ofthe plurality of transistors at the top surface of the siliconsubstrate.
 12. A semiconductor structure formed in a silicon substratecomprising: a plurality of transistors each comprising a source regionand a drain region formed in the silicon top layer and a gate formedover the source and drain regions; a diamond insulation layer formedadjacent to sidewalls of the gates of each of the plurality oftransistors at the top surface of the silicon substrate; and a pluralityof thermally conductive diamond sidewall spacers disposed at thesidewalls of each gate and contacting the source and drain regions. 13.A cooling structure for cooling a semiconductor transistor having asource region and a drain region formed in the top of a siliconsubstrate and a gate disposed on the top surface of the siliconsubstrate and contacting the source and drain regions comprising: afirst diamond sidewall spacer formed on one sidewall of the gate andcontacting the source region; and a second diamond sidewall spacerformed on a second sidewall of the gate and contacting the drain region.14. The structure of claim 13 further comprising a diamond insulationlayer formed adjacent to each gate at the top of the silicon substrate.15. A cooling structure for cooling at least one of a plurality ofsemiconductor devices formed in a substrate having a top silicon layer,a buried oxide layer underlying the top silicon layer, and a bulksilicon region underlying the buried oxide layer, comprising: aplurality of independent thermal trenches filled with thermallyconductive and electrically nonconductive diamond, each trench beingformed adjacent at least one of said plurality of semiconductor devicesand extending from the top surface of the silicon top layer, through theburied oxide layer, and to the bulk silicon region and being in thermalcontact with at least one of the devices, wherein said devices comprisetransistors, each having a source region and a drain region formed inthe top of a silicon substrate and a gate disposed on the top surface ofthe silicon substrate and contacting the source and drain regions,wherein said structure further comprising a plurality of first diamondsidewall spacers, each being formed on a first sidewall of a gate andcontacting the source region, and a plurality of second diamond sidewallspacers, each being formed on the second sidewall of the gate andcontacting the drain region.
 16. The structure of claim 15 wherein saidstructure further comprises a diamond insulation layer disposed betweenadjacent devices at the top of the silicon substrate.